The present invention relates to novel ultra-large porous compositions, and organometallic catalysts immobilized on these compositions, including asymmetric organometallic catalysts. Reactions performed by these catalysts include hydrogenation, hydroformylation, carbonylation, carbon-carbon coupling reactions, as well as asymmetric reactions such as asymmetric hydrogenation.
Many industrially important reactions, especially in the fine chemicals and pharmaceuticals industries, involve the use of expensive homogeneous catalysts. The homogeneous catalysts show good activity and can be tailored to allow for a high degree of product selectivity.
Such active and selective homogeneous catalysts are expensive to synthesize, and typically are very difficult to recover from reaction mixtures. The complexity of catalyst synthesis and separation procedures leads to high costs due to capital investment in high-temperature distillation and/or liquid-liquid separation equipment used in the separation of the catalyst from the reaction mixture, and due to operating costs incurred by rapid catalyst loss and deactivation. Overcoming or decreasing these obstacles is necessary to meet growing demand for highly specific molecular products, especially in life sciences industries. This demand has driven the commercial desirability of organometallic catalysts for reactions involving carbon-carbon bond formation (e.g., Heck and Suzuki coupling) and enantioselective hydrogenations.
Although heterogeneous catalysts do not afford comparable performance, these catalysts offer other advantages such as ease of catalyst recovery. In order to create an easily separable and reusable catalyst, a number of different techniques have been developed to xe2x80x9cheterogenizexe2x80x9d homogeneous transition metal catalysts for various catalytic reactions. These techniques involve (i) dissolution of modified homogeneous catalysts in a liquid phase which is not miscible with the reaction solvent, and subsequent support of the non-soluble phase on solid particles, or (ii) covalent linkage of catalyst molecules to silica beads and polymer matrices. These methods, however, result in low surface area catalysts that have only a small fraction of active component exposed to the reaction mixture. These limitations can lead to long reaction times and large reactor volumes.
The synthesis of stereospecific products also presents a great need in the life sciences industry. There are extensive literature reports on the preparation of new asymmetric catalysts through immobilization of chiral metal complexes to solid supports. Immobilization typically involves a covalent linkage via functionalized chiral ligands. This method is successful to some extent as leaching of expensive chiral ligand can be minimized. However, this method does have its drawbacks. The majority of chiral ligands does not contain functional groups that allow direct linkage to solid supports such as silica gels. Modifying the chiral ligand with a functional group is often expensive, involving lengthy synthetic steps, and is detrimental to the selectivity of the catalyst. Furthermore, the sensitivity of the functional groups (i.e. trialkoxysilyl group) towards water tends to complicate synthesis.
Thus, it remains a challenge to prepare catalysts that exhibit high activity and selectivity through immobilization of the catalysts to a surface capable of being easily recovered from solution. It also remains a challenge to prepare asymmetric catalysts having high enantioselectivity. In addition, the immobilized catalysts should ideally be stable to a wide variety of catalytic conditions.
One aspect of the present invention provides an article comprising an organometallic catalyst immobilized on a polymer-templated composition having at least about 50% of a total pore volume comprising pores with a mean diameter of at least about 50 xc3x85.
Another aspect of the present invention provides an article comprising an asymmetric organometallic catalysts immobilized on a surface via an achiral ligand.
Another aspect of the present invention provides a method for making a catalysts. A method comprises forming a mesoporous composition via a polymer template, the mesoporous composition having at least about 50% of a total pore volume comprising pores with a mean diameter of at least about 50 xc3x85. The method also comprises immobilizing an organometallic catalysts on the mesoporous composition.
Another aspect of the present invention provides a method for performing a catalytic reaction. The method comprises contacting a catalyst with a substrate. The catalyst comprises an organometallic complex immobilized on a mesoporous composition having at least about 50% of a total pore volume comprising pores with a mean diameter of at least about 50 xc3x85.
Another aspect of the present invention provides an article comprising a polymerization catalyst immobilized on a porous composition. The composition has pores of a predetermined mean diameter to define a molecular weight distribution of a polymer.
Another aspect of the present invention provides an article comprising catalyst immobilized on a porous composition. The composition has pores of a predetermined mean diameter to influence stereoselectivity.
Another aspect of the present invention provides a system comprising a plurality of supports. Each support comprises a composition having pores of a mean diameter of at least about 50 xc3x85.
Other advantages, novel features, and objects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings, which are schematic and which are not intended to be drawn to scale. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention.